CN101364631A

CN101364631A - Nonpolar GaN film and growth method thereof

Info

Publication number: CN101364631A
Application number: CNA2008102004586A
Authority: CN
Inventors: 周健华; 郝茂盛; 颜建锋; 潘尧波; 周圣明
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS; Irico Group Corp; Epilight Technology Co Ltd
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS; Irico Group Corp; Epilight Technology Co Ltd
Priority date: 2008-09-25
Filing date: 2008-09-25
Publication date: 2009-02-11
Anticipated expiration: 2028-09-25
Also published as: CN101364631B

Abstract

The invention provides a nonpolar GaN film and the growth method thereof. The method comprises the following steps: first, heating to a temperature of 800 DEG C to 900 DEG C and growing a low-temperature protective layer on a lithium aluminate (LiAlO2) substrate in a metal organic chemical vapor deposition (MOCVD) system under the protection of N2, wherein the pressure in the reaction chamber of the low-temperature protective layer is 150 to 500 torr, and the flow rate of trimethyl gallium (TMGa) is 1 to 50 sccm, and the molar flow rate corresponding to the flow rate is 4E-6mole/min to 3E-4mole/min; then, reducing the pressure to 100 to 300 torr, heating to 1000 DEG C to 1100 DEG C and proceeding with the growth of the undoped gallium nitride (U-GaN) layer, wherein the flow rate of TMGa is 10 to 200 sccm, and the corresponding molar flow rate thereof is 4E-5mol/min to 1E-3mole/min; further heating to 1150 DEG C to 1200 DEG C, and growing the high-temperature U-GaN for about 100 nm; and then further cooling to 1000 DEG C to 1100 DEG C and growing U-GaN. The growth of the low-temperature protective layer protects the LiAlO2 substrate against the damage caused by the high temperature, and the method aims to improve the surface smoothness of the grown GaN film by heating U-GaN to a high temperature for a short term.

Description

A kind of nonpolar GaN film and growing method thereof

Technical field

The present invention relates at a kind of novel substrate LiAlO ₂Use yield production type MOCVD board growing nonpolar GaN film and growing method thereof on the material.

Background technology

The new generation of semiconductor material that with GaN is representative has obtained people's extensive concern with characteristics such as its wide direct band gap (Eg=3.4eV), high heat conductance, high rigidity, high chemical stability, low-k, radioresistances, in fields such as solid-state illumination, solid state laser, optical information storage, ultraviolet detectors huge application potential is arranged all.Calculate by China's electricity consumption situation in 2002,, can save the energy output of the three gorges hydropower plant in 1 year, huge economy, environment and social benefit are arranged if adopt solid-state illumination to substitute conventional light source; And according to USDOE's measuring and calculating, by 2010, the whole America semiconductor lighting industry output value will reach 50,000,000,000 dollars.Aspect the optical information storage, can increase substantially optical storage density based on the solid blue light laser of GaN.Just because of these advantages, GaN and alloy thereof are placed high hopes.High brightness InGaN/GaN quantum well structure LEDs commercialization.

Backing material has material impact for the quality of epitaxial film.GaN body monocrystalline material growth is very difficult at present, reports that GaN is that 60-70kbar, temperature are also not melt under 2300 ℃ at pressure.Growth conditions is HTHP normally, costs dearly, and is unfavorable for commercialization, and therefore present application is to do heteroepitaxy at c on sapphire mostly.Using c is that the lattice mismatch of itself and GaN film is up to 13.6% to a sapphire significant drawback, though can remedy this shortcoming by the resilient coating technology, but serious like this mismatch still can cause having in the epitaxial film highdensity defective, thereby reduces device efficiency.In addition, the GaN film is normally along its polar axis c direction of principal axis growth, and the powerful internal electric field that is produced by spontaneous polarization and piezoelectric effect has reduced luminous efficiency widely.Adopt novel LiAlO ₂Substrate is expected to solve this two problems.LiAlO ₂Substrate and GaN film lattice mismatch are little, have only 1.4%, and at LiAlO ₂Last growth be nonpolar GaN film, can eliminate the restriction of internal electric field for luminous efficiency.

Summary of the invention

The technical problem to be solved in the present invention is: a kind of growing method of nonpolar GaN film is provided, and it utilizes MOCVD system synthetically grown nonpolar GaN film on the lithium aluminate substrate.

In order to solve the problems of the technologies described above, the present invention adopts following technical scheme: a kind of nonpolar GaN film, it utilizes the MOCVD system at LiAlO ₂Synthetically grown on the substrate, this film comprises LiAlO ₂The low-temperature protection layer of substrate and growth successively, U-GaN (non-doped gallium nitride) layer, high temperature U-GaN layer and another U-GaN layer.

The present invention further comprises a kind of growing method of nonpolar GaN film, and this method may further comprise the steps:

Step 1: in the MOCVD system, under the N2 protection, be warmed up to 800-900 ℃; growing low temperature protective layer on the lithium aluminate substrate; low-temperature protection stressor layer 150-500torr, TMGa flow 1-50sccm is corresponding to molar flow: 4E-6mole/min-3E-4mole/min.

Step 2: reduce pressure to 100-300torr, be warmed up to 1000-1100 ℃ of growth U-GaN layer, TMGa flow 10-200sccm is corresponding to molar flow: 4E-5mol/min-1E-3mole/min;

Step 3: be warmed up to 1150-1200 ℃ again, growth high temperature U-GaN layer 100nm under this temperature;

Step 4: cool to 1000-1100 ℃ of another U-GaN layer of growth again.

As one of a preferred embodiment of the present invention, in step 1, before the growth beginning, at first the lithium aluminate substrate surface is carried out situ heat treatment under 600-900 ℃.

In sum, the invention provides a kind of nonpolar GaN film and growing method thereof, it utilizes the MOCVD system at LiAlO ₂Synthetically grown nonpolar GaN film on the substrate, by the growing low temperature protective layer, protection lithium aluminate substrate is not destroyed by high temperature, and high temperature U-GaN layer can improve the surface smoothness of Grown GaN.

Description of drawings

Fig. 1 is the present invention's process conditions schematic diagram in the flow process of growing;

Fig. 2 is a structural representation of the present invention.

Embodiment

Further specify concrete implementation step of the present invention below in conjunction with accompanying drawing:

A kind of nonpolar GaN film, it utilizes MOCVD system synthetically grown on the lithium aluminate substrate, and this film comprises low-temperature protection layer, U-GaN layer, high temperature U-GaN layer and another U-GaN layer of growing successively on the lithium aluminate substrate.

A kind of growing method of nonpolar GaN film is in the MOCVD system, at N ₂Protection down; (can carry out situ heat treatment at 600-900 ℃; can not handle yet) be warmed up to 800-900 ℃; the growing low temperature protective layer; the low-temperature protection stressor layer is than higher (150-500torr); lower (the 1-50sccm of TMGa flow-rate ratio; corresponding to molar flow: 4E-6mole/min-3E-4mole/min), reduce pressure (100-300torr) then, be warmed up to 1000-1100 ℃ of continued growth U-GaN layer; higher (the 10-200sccm of TMGa flow-rate ratio;,, and then be warmed up to 1150-1200 ℃ corresponding to molar flow: 4E-5mol/min-1E-3mole/min); about 100nm that grows, and then cool to 1000-1100 ℃ of growth U-GaN.

Grown a complete single layer structure like this.The purpose of low-temperature protection layer is: protection lithium aluminate substrate is not destroyed by high temperature, and low-temperature protection layer TMGa flow must be smaller, and the quality of low-temperature protection layer is unlikely to very poor like this.The purpose of the of short duration highest temperature (1150-1200 ℃) is to improve the surface smoothness of Grown GaN film, and this time can not be oversize, and oversize meeting destroys substrate, and too short not having again improved surperficial effect.

If the lithium aluminate substrate is (100) face, institute's Grown GaN thin film alignment is m (a 1010) face so; If the lithium aluminate substrate is (302) face, institute's Grown GaN thin film alignment is a (a 1120) face so.

Main feature:

1, can not heat-treat;

2, the low-temperature protection layer, temperature is lower, and pressure ratio is higher, and the TMGa flow-rate ratio is lower, and growth rate is slow;

3, the U-GaN layer, temperature is higher, and pressure is lower, and the TMGa flow-rate ratio is higher, and growth rate is than very fast;

4, high temperature U-GaN layer, temperature is the highest, and time ratio is shorter, improves the effect on surface.

Above embodiment is the unrestricted technical scheme of the present invention in order to explanation only.Any technical scheme that does not break away from spirit and scope of the invention all should be encompassed in the middle of the patent claim of the present invention.

Claims

1. nonpolar GaN film; it utilizes MOCVD system synthetically grown on the lithium aluminate substrate, it is characterized in that: this film is included in low-temperature protection layer, U-GaN (non-doped gallium nitride) layer, high temperature U-GaN layer and another U-GaN layer of growing successively on the lithium aluminate substrate.

2. the growing method of a nonpolar GaN film as claimed in claim 1 is characterized in that, this method may further comprise the steps:

Step 1: in the MOCVD system, at N ₂Protection is warmed up to 800-900 ℃ down, growing low temperature protective layer on the lithium aluminate substrate, and low-temperature protection stressor layer 150-500torr, TMGa flow 1-50sccm is corresponding to molar flow: 4E-6mole/min-3E-4mole/min.

Step 4: cool to 1000-1100 ℃ of another U-GaN layer of growth again.

3. the growing method of a kind of nonpolar GaN film as claimed in claim 1 is characterized in that: in step 1, before the growth beginning, at first the lithium aluminate substrate surface is carried out situ heat treatment under 600-900 ℃.